Trellis-based Iterative Decoding of Block Codes for Satellite ATM. PDF Download
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Languages : en
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Author: Shu Lin
Publisher: Springer Science & Business Media
ISBN: 1461557453
Category : Technology & Engineering
Languages : en
Pages : 290
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As the demand for data reliability increases, coding for error control becomes increasingly important in data transmission systems and has become an integral part of almost all data communication system designs. In recent years, various trellis-based soft-decoding algorithms for linear block codes have been devised. New ideas developed in the study of trellis structure of block codes can be used for improving decoding and analyzing the trellis complexity of convolutional codes. These recent developments provide practicing communication engineers with more choices when designing error control systems. Trellises and Trellis-based Decoding Algorithms for Linear Block Codes combines trellises and trellis-based decoding algorithms for linear codes together in a simple and unified form. The approach is to explain the material in an easily understood manner with minimal mathematical rigor. Trellises and Trellis-based Decoding Algorithms for Linear Block Codes is intended for practicing communication engineers who want to have a fast grasp and understanding of the subject. Only material considered essential and useful for practical applications is included. This book can also be used as a text for advanced courses on the subject.
Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781728906683
Category : Science
Languages : en
Pages : 26
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For long linear block codes, maximum likelihood decoding based on full code trellises would be very hard to implement if not impossible. In this case, we may wish to trade error performance for the reduction in decoding complexity. Sub-optimum soft-decision decoding of a linear block code based on a low-weight sub-trellis can be devised to provide an effective trade-off between error performance and decoding complexity. This chapter presents such a suboptimal decoding algorithm for linear block codes. This decoding algorithm is iterative in nature and based on an optimality test. It has the following important features: (1) a simple method to generate a sequence of candidate code-words, one at a time, for test; (2) a sufficient condition for testing a candidate code-word for optimality; and (3) a low-weight sub-trellis search for finding the most likely (ML) code-word. Lin, Shu and Fossorier, Marc Goddard Space Flight Center NAG5-931; NAG5-2938
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722916640
Category :
Languages : en
Pages : 24
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For long linear block codes, maximum likelihood decoding based on full code trellises would be very hard to implement if not impossible. In this case, we may wish to trade error performance for the reduction in decoding complexity. Sub-optimum soft-decision decoding of a linear block code based on a low-weight sub-trellis can be devised to provide an effective trade-off between error performance and decoding complexity. This chapter presents such a suboptimal decoding algorithm for linear block codes. This decoding algorithm is iterative in nature and based on an optimality test. It has the following important features: (1) a simple method to generate a sequence of candidate code-words, one at a time, for test; (2) a sufficient condition for testing a candidate code-word for optimality; and (3) a low-weight sub-trellis search for finding the most likely (ML) code-word. Lin, Shu and Fossorier, Marc Goddard Space Flight Center NAG5-931; NAG5-2938...
Author: M. Reza Soleymani
Publisher: Springer Science & Business Media
ISBN: 0306476770
Category : Technology & Engineering
Languages : en
Pages : 232
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6. 5 137 7 Performance of BTCs and 139 their Applications 7. 1 Introduction 139 7. 2 Some Results from the Literatures 139 7. 3 Applications of Block Turbo Codes. 142 7. 3. 1 Broadband Wireless Access Standard 144 7. 3. 2 Advanced Hardware Architectures (AHA) 145 7. 3. 3 COMTECH EF DATA 147 7. 3. 4 Turbo Concept 149 7. 3. 5 Paradise Data Com 150 Summary 7. 4 151 8 Implementation Issues 153 8. 1 Fixed-point Implementation of Turbo Decoder 153 8. 1. 1 Input Data Quantization for DVB-RCS Turbo Codes 155 8. 1. 2 Input Data Quantization for BTC 157 8. 2 The Effect of Correction Term in Max-Log-MAP Algorithm 159 8. 3 Effect of Channel Impairment on Turbo Codes 163 8. 3. 1 System Model for the Investigation of Channel Impairments 163 8. 3. 2 Channel SNR Mismatch 164 8. 3. 2. 1 Simulation Results 165 8. 3. 3 Carrier Phase Recovery 170 8. 3. 3. 1 The Effect of Phase Offset on the Performance of RM Turbo Codes 170 8. 3. 3. 2 The Effect of Preamble Size on the Performance of RM Turbo Codes 170 8. 3. 3. 3 Simulation Results 170 8. 4 Hardware Implementation of Turbo Codes 171 8. 5 Summary 175 9 177 Low Density Parity Check Codes 9. 1 Gallager Codes: Regular Binary LDPC Codes 177 9. 2 Random Block Codes 178 9. 2. 1 Generator Matrix 179 9. 2.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722916787
Category :
Languages : en
Pages : 50
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In a coded communication system with equiprobable signaling, MLD minimizes the word error probability and delivers the most likely codeword associated with the corresponding received sequence. This decoding has two drawbacks. First, minimization of the word error probability is not equivalent to minimization of the bit error probability. Therefore, MLD becomes suboptimum with respect to the bit error probability. Second, MLD delivers a hard-decision estimate of the received sequence, so that information is lost between the input and output of the ML decoder. This information is important in coded schemes where the decoded sequence is further processed, such as concatenated coding schemes, multi-stage and iterative decoding schemes. In this chapter, we first present a decoding algorithm which both minimizes bit error probability, and provides the corresponding soft information at the output of the decoder. This algorithm is referred to as the MAP (maximum aposteriori probability) decoding algorithm. Lin, Shu and Fossorier, Marc Goddard Space Flight Center NAG5-931; NAG5-2938...
Author: Huijun Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 240
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Abstract: In this dissertation, we focus on three issues of the trellis based iterative decoding: First, the complexity issue of Turbo code is considered. We propose a constrained iterative decoder to reduce the decoding complexity. An additional interleaver is introduced at the encoder. At the decoder, we first use Cyclic Redundance Code (CRC) to detect which bits are already correctly decoded during early iterations. With knowledge of the positions of these correct bits, the constrained decoding algorithm is designed to reduce the number of the state transitions in the component code trellis and help the decoding of other bits in later iterations. In this way, the constrained iterative decoder achieves significant complexity reduction and still satisfying performance. Second, the iterative decoding algorithm is redesigned for Turbo code implemented Distributed Source Coding (DSC). When used in DSC, the Turbo decoder encounters a combined Binary Symmetric Channel (BSC) and Addictive White Gaussian Noise (AWGN) distortion. The existing iterative decoding algorithm based on AWGN distortion assumption causes performance degradation. By redefining the channel reliability values, the modified iterative decoding algorithm matches the BSC-AWGN scenario well and improves the performance. Third, we propose a reliable source transmission coding and decoding scheme. A serially concatenated source and space time modulated coding structure is used. Variable Length Code (VLC) with error resilient capability is adopted at the application layer. Space Time Trellis Code (STTC) is used to provide high bandwidth efficiency at the physical layer. An iterative joint source space time decoder is designed including the symbol level space time Maximum A Posteriori (MAP) decoder, the bit level VLC MAP decoder and the Viterbi VLC decoder. Critical issues such as STTC MAP algorithm with nonseparable systematic information, VLC MAP algorithm in absence of channel output, VLC Viterbi algorithm based on the bit level trellis and extrinsic information conversion and exchange between bit domain and symbol domain are addressed. The decoding performance of different frame sizes and different component VLCs and STTCs, the rate allocation between the source code and the space time code and the performance in presence of channel estimation errors are discussed in this dissertation.
Author: Bo Yin
Publisher:
ISBN:
Category : Coding theory
Languages : en
Pages : 0
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Forward Error Correction (FEC) technique provides a method to detect and correct errors in transmitted data. It is also a valuable technique to reduce the power requirement, thus have an important role in these systems. This reduction in power requirement is achieved at the expense of an increase in bandwidth requirement. The objective is usually to find error control techniques that give good tradeoff between power and bandwidth requirements. In this thesis, we present results for FEC technique using Turbo Block Codes and Turbo Product Codes. It is shown that these codes, not only in theory but also in hardware implementation, are capable of providing significant performance gains over other error-correction schemes. This thesis investigates Trellis based iterative decoding techniques applied to concatenated coding schemes, Turbo Block Codes. We use RM(n, k) to construct 2-D and multi-dimensional Turbo Block Codes. Our objective is to get high code rates and long block sizes for more bandwidth efficiency and improving the performance of the optimised maximum a posterior decoding algorithm.
Author: Frédéric Fontaine (Michel)
Publisher:
ISBN:
Category :
Languages : en
Pages : 242
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781720619314
Category :
Languages : en
Pages : 28
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The MAP algorithm is a trellis-based maximum a posteriori probability decoding algorithm. It is the heart of the turbo (or iterative) decoding which achieves an error performance near the Shannon limit. Unfortunately, the implementation of this algorithm requires large computation and storage. Furthermore, its forward and backward recursions result in long decoding delay. For practical applications, this decoding algorithm must be simplified and its decoding complexity and delay must be reduced. In this paper, the MAP algorithm and its variations, such as Log-MAP and Max-Log-MAP algorithms, are first applied to sectionalized trellises for linear block codes and carried out as two-stage decodings. Using the structural properties of properly sectionalized trellises, the decoding complexity and delay of the MAP algorithms can be reduced. Computation-wise optimum sectionalizations of a trellis for MAP algorithms are investigated. Also presented in this paper are bi-directional and parallel MAP decodings.Lin, ShuGoddard Space Flight CenterALGORITHMS; DECODING; LINEAR SYSTEMS; PROBABILITY THEORY; ERRORS; COMPUTATION
